Why do we laugh? Well it’s funny you should ask, but this question was suggested by reader Andrew Martin, and it is a very interesting one to investigate. For what at first seems like a simple question turns out to require a surprisingly complex answer – one that takes us on a journey into the very heart of trying to understand human nature.

Most people would guess that we laugh because something is funny. But if you watch when people actually laugh, you’ll find this isn’t the case. Laughter expert Robert Provine spent hours recording real conversations at shopping malls, classrooms, offices and cocktail parties, and he found that most laughter did not follow what looked like jokes. People laughed at the end of normal sentences, in response to unfunny comments or questions such as “Look, it’s Andre,” or “Are you sure?”. Even attempts at humour that provoked laughter didn’t sound that funny. Provine reports that the lines that got the biggest laughs were ones such as “You don’t have to drink, just buy us drinks,” and “Do you date within your species?”. I guess you had to be there.

Brain triggers
So if we want to understand laughter, perhaps we need to go deeper, and look at what is going on in the brain. The areas that control laughing lie deep in the subcortex, and in terms of evolutionary development these parts of the brain are ancient, responsible for primal behaviours such as breathing and controlling basic reflexes. This means laughter control mechanisms are located a long way away from brain regions that developed later and control higher functions such as language or even memory.

Perhaps this explains why it is so hard to suppress a laugh, even if we know it is inappropriate. Once a laugh is kindled deep within our brains these ‘higher function’ brain regions have trouble intervening. And the reverse is true, of course, it is difficult to laugh on demand. If you consciously make yourself laugh it will not sound like the real thing – at least initially.

There is another fundamental aspect to laughing. All humans laugh, and laughter always involves a similar pattern of whooping noises. Deaf people who have never heard a sound still make laughing noises. The laughing noises produced by humans share many of the acoustic properties of speech, further evidence laughter is hijacking the brain and body apparatus that we use for breathing and talking.

But this does not fully answer the original question. Even if we identified the precise brain areas associated with laughing, even if we were able to make someone laugh by stimulating part of their brain (which can be done), we still don’t know what makes people laugh. Yes, we know about the effect, but what about the cause, that is, the reason why we laugh in the first place?

Shared joke
To answer this, perhaps we need to look outwards, to look at the social factors at play when people laugh. I’ve already mentioned Provine’s study of laughter in its natural context. Provine showed that laughter is used to punctuate speech, it doesn’t just interrupt at random. This suggests that it plays a communicative role – it isn’t just some independent process that happens to us while we are talking to someone. He also found that the speaker typically laughs more than the audience, and that laughter was most common in situations of emotional warmth and so-called ‘in-groupness’. Again, all strongly suggesting that laughter has an important social role. And it is not always used for positive reasons. For all the good feeling that goes with laughing with someone, there is also a dark side, when someone is laughed at to belittle or show disdain.

Perhaps the most important social feature of laughter is how contagious it is. Just listening to someone laugh is funny. To test this, try keeping a straight face while watching this video of a man tickling a gorilla. You can even catch laughter from yourself. Start with a forced laugh and if you keep it up you will soon find yourself laughing for real.

What these observations show is that laughter is both fundamentally social, and rooted deep within our brains, part and parcel of ancient brain structures. We laugh because we feel like it, because our brains make us, and because we want to fit in socially. All these things are true. But biologists distinguish at least four fundamental types of answer you can give to explain behaviour: “why did it evolve?”; “how did it evolve?”; “How does it develop across the lifespan?” and “how does it work?”.

This column has given some answers to the first question (laughter evolved for social interaction) and the last question (laughter is controlled by evolutionary ancient brain centres that control breathing and speech), but even with the beginnings of answers to these two questions, the other two are far from being answered. Each time we get closer to an answer for a fundamental question, it deepens our appreciation of the challenge remaining to answer the others.

Thank you to Andrew Martin for suggesting the topic. If you have your own suggestions please send them to tom@mindhacks.com

Hi Tom,
I have a new project that will have a go at answering the question “How does laughter develop across lifespan?” The Baby Laughter project (http://babylaughter.net) will survey parents of babies and toddlers to see if there are developmental changes in what makes babies laugh at different ages.

The aims are two-fold. Firstly to see how laughter changes in those early years and secondly to see if those changes track other milestones in cognitive development. My hope is that we will find some evidence that babies laughter is a good index of what they understand about the world at different ages. You can’t laugh if you don’t get the joke. But I also expect to confirm the findings in the adult literature (Provine, 2000) that most laughter is primarily social in nature.

We just got ethical approval this week but there are a few more things to do before the survey launches. So watch this space.

Liked it. Not an easy topic to translate from the currently vague hypothesis. I’ve seen some annoying media articles claiming that non-primate animals have a “sense of humor”. While I think play is valid, we don’t even define humor outside of the primate world, so far as I can tell.

My former coworker had an especially convincing fake laugh and used it often for when people told not so funny jokes. (The laugh was not what you’d expect – it was slow, deliberate and understated).

It says that laughing comes from the same “apparatus” that is used for breathing and talking. I’m curious what part of the brain is being referred to and how this was determined. The idea that laughing enforces or detrimizes certain aspects of communication (speech or statements/ideas) is very interesting. If this behavior or mechanism of behavior is “innate”, it is curious to incorporate the idea that it is evokutionarily beneficial somehow. Possibly to communicate with fellow species or to show we are not aggressive at that time. Such as the smile… Not baring our incisors, but covering them with our lips (to show we are not aggressive)… Curious indeed